A wireless communication device that uses a frequency band such as an ISM (Industrial Scientific and Medical) band may experience disturbance on wireless communications due to a radio wave generated by an interference source using the same frequency band such as a microwave oven and medical devices. In order to avoid such disturbances, it is necessary to detect a signal of a radio wave from an interference source from received radio signals and check presence or absence of the interference source.
As a method of detecting a signal of the radio wave from the interference source, some detection methods use the periodic nature of the operation of the interference source. For example, a microwave oven which is one of the interference sources can be classified into a transformer type and an inverter type on the basis of the driving system. Both types of microwave ovens emit radio waves by alternately repeating oscillation and stoppage of a magnetron inside of the microwave oven on the basis of the period (cycle) of an AC source that supplies power thereto. Accordingly, the signal of a radio wave from a microwave oven has a periodic nature. As a result, a signal of a radio wave from an interference source can be detected by detecting a signal having a periodic nature from received radio signals.
However, a drawback is that a signal has to be received for a plurality of times in order to determine the periodic nature of the signal and the time required for the detection is prolonged. Also, in the case of an inverter microwave oven inside of which switching is performed, the operation of the microwave oven may be temporarily stopped depending on the content and situation of cooking, making it difficult to correctly determine the periodic nature of the signal.